Reproduction steps:
1. Open project in "ReproProject.zip"
2. Open "SampleScene.unity"
3. There is a TMP password Input Field in the Scene with "Hide Mobile Input" checked
4. The Text Field below displays what is written in the TMP password Input Field
5. Build the project for iOS and deploy it to an iOS device
6. Select the TMP Input Field and enter some text using the native iOS keyboard
7. De-focus the TMP Input Field by clicking on the background of the Application
8. Focus on the TMP Input field again and enter 2 characters

Unexpected behaviour: the character that was entered first in step 8 disappears (check note 1, 3)

Reproducible with: 2019.3.15f1, 2020.1.0b10, 2020.2.0a1, 2020.2.0a13
Not reproducible with: 2018.4.22f1, 2020.1.0a26

Devices tested:
Reproducible with:
VLNQA00310 iPad Pro 12.9 (iOS 13.4.1)
Not reproducible with:
N/A, Samsung Galaxy S9 (SM-G960F), Android 8.0.0, CPU: Exynos 9 Series 9810, GPU: Mali-G72
VLNQA00313, Huawei Y6 Ⅱ Compact (HUAWEI LYO-L01), Android 5.1, CPU: MediaTek MT6735, GPU: Mali-T720
VLNQA00140, Samsung Galaxy S4 (GT-I9505), Android 5.0.1, CPU: Snapdragon S4 Plus MSM8960, GPU: Adreno (TM) 320

Notes:
1. This issue can be reproduced multiple times once the game has started by entering text in Input Field, defocusing it, focusing it and repeating from the part "entering text"
2. The issue has been backported to 2019.3, 2020.1 streams
3. A video is attached